Patients with locally advanced unresectable malignancies often cannot be effectively treated with conventional cytoreductive or curative surgical procedures because of extent of tumor, poor general clinical condition and performance status, or patient refusal to undergo cosmetically unacceptable surgery. Additionally, many of these patients have initially been treated with chemotherapy and/or radiotherapy without success and no further effective therapeutic avenues exist. In such patients, non-invasive, in situ coagulation of graded volumes of the tumor may be an effective therapeutic modality. Focused ultrasound has been shown to be capable of transcutaneously inducing discrete areas of coagulatic necrosis of precisely controllable size and at predetermined locations within the central nervous system without mishap. It is proposed that this technique be modified and tested to enable its future extension to effect diminution of tumor burden in selected patients whose tumors, general condition and previous treatment all combine to provide a grim prognostic outcome. Non-invasive, transcutaneous cytoreduction of graded volumes of the tumor, followed by tumor-bed hyperthermia is expected to be not only palliative by alleviating local tumor effects but may also reverse immunodepression and nutritional impairment and thus lead to tumor control. Preliminary data on safety and efficacy of the procedure in superficial and deep tumors will be obtained in transplanted murine tumors and spontaneous tumors in dogs and cats.